Methods of suppressing foam on paper stock



Patented Oct. 14, 1947 LIETHODS F SUPPRESSING FOAM ON PAPER STOCK Francis G. Rawling, Luke, Md., assgnor to West Virginia Pulp and Paper Company, New York, 1 N. Y., a corporation of Delaware No Drawing. Application August 22, 1941,

Serial No. 407,903

4 Claims. (c1. 92,-40) I My present invention relates to an improved method of suppressing foam on the Fourdrinier wire when the paper is formed out of pulp containing rosin and alum size. As is well known in the art, the action of foam, which consists of bubbles of varying size, is to create marks in the finished paper which are particularly noticeable when the paper is examined by light transmitted through it. Commonly steam sprays are used to break up bubble formation either on the Fourdrinier wire or in the flow boxes, and sometimes at other places behind the flow box, as for example, on the riflies leading thereto. The force of the steam sprays above the Fourdrinier wire. however. tends to spatter the stock and spoil the formation of the sheet.

I have now discovered that a principal reason for the formation of foam is the formation of calcium reslnate due to the presence of the rosin size in water used in pulping the stock which commonly is to some degree hard, i. e., containing calcium salts in solution, the calcium resinate formed acting as a stabilizer for the presumably colloidal matter causing persistence of bubbles. By introducing onto the surface of the web as it is being formed a suitable reagent which depresses the concentration of calcium ions at the surface of the web (and hence the quantity of calcium resinate in solution there), the foam formation is satisfactorily minimized. The type of reagent which I have found to work best is a dilute solution of alkali metal (including ammonium) salt yielding anions which remove calcium ions and hence destroy the activity of the calcium resinate, or any other calcium compound responsible for the bubble formation. The solution which I prefer for the purpose is sodium or other alkali metal stearate yielding stearate ions in solution, although other soaps may be used, as hereinafter mentioned. Preferably the reagent is added in the form of a spray upon the web on the Fourdrinier wire a short distance beyond the fiow box, as for example, just rearward of the dandy roll. The foam occurring here is commonly referred to as "dandy bubbles." A concentration of solution that I have found satisfactory is from one-half to two pounds of sodium stearate in fifty gallons of water which is sprayed upon the Fourdrinier wire at the region mentioned. The concentration of the sprayed solution is, however, not critical within wide limits. The actual quantity of sodium stearate used is relatively slight. Thus, in a Fourdrinier having a capacity of 35 tons of paper per twenty-four hours I have found seven pounds of sodium stearate for this period to be 2 sufflcient; it being understood, however, that the operator will vary the amount to suit the conditions that he is dealing with (notably, the hardness of the water), whereby this amount will vary considerably.

As above pointed out, the action of the sprayed reagent'is to depress the concentration of calcium ions at the surface of the web, thus enabling the surface of the sheet to be formed substantially free of foam marks before the concentration of calcium resinate can be restored there. A very minute amount of the reagent is therefore required. If, on the other hand, it were attempted to add the reagent to the furnish to the machine, a very much greater quantity would be needed inas much as it would be necessary to suppress calcium ions throughout the entire furnish.

As a source of the effective agent, common laundry soap may be used although I find that of the soap-forming fatty acids the soluble stearates are the most effective; the palmitates are less so, for example. The soluble arachidates and cerotates are likewise effective, but are much more expensive than the soluble stearates. I therefore prefer to use a solution of sodium stearate. It is obvious that unless the anion added forms a calcium salt substantially more insoluble than calcium resinate, the reagent will not be effective. I have further found that the use of sodium stearate, for example, not only prevents troublesome bubble formation, but smooths out ripples and:

waves in the stock whereby a smoother sheet is formed.

I claim:

l. The method of suppressing foam formed during the formation of a paper web on the Fourdrinier wire, when such web is formed of stock containingrosin size and sufficient calcium resinate to cause foaming, which consists in spraying on the web on the Fourdrinier wire before the formation of the sheet is completed a dilute solution of an alkali metal stearate and thereby forming an insoluble calcium stearate on the surface of said stock.

2. The method of suppressing foam formed during the formation of a paper web on the Fourdrinier wire when such web is formed of stock containing rosin size and sufilcient calcium resinate to cause foaming, which consists in spraying on the web on the Fourdrinier wire before the formation of the sheet is completed a dilute solution of a water-soluble fatty acid soap and thereby forming on the surface of the stock the correponding calcium soap which is insoluble.

3. The method of suppressing foam formed during the formation of apeper web on'the' Fourdrinier wire when such webis formed of stock containing rosin size and sumcient calcium resinate to cause foaming, which consists in spraying on the web on the .Fourdrinierwwire betore the formation of the sheet, is completed asolutioncontaining a fatty acid anion capable of depressing substantially the concentration of calcium ions in solutionin thestock, and forming antinsoluble calcium soap onthe surface of "the stools the region before the dandy rolladilutesolution of a water-soluble vfatty acidsoap, thereby forming on the surface of the stockthe corresponding calcium soap which isvinsolubie.v

, FRANCIS; G; RAWLING.

REFERENCES CITED The following references are of.recor'd in the file of this patent:

UNITED STATES PATENTS Number Name Date 1 ,839,449 Sutermeister'et a1. J an. 5', 1932 1,986,291 'Schur Jan. 1, 1985- 989425 Rogers ;-1 Apr; 11,1911 2,209,591 Barnes July '30, 1940 1,958,202 Novak May'B, 1934 2,093,576 Seggessemann Sept. 21,193! 2,102,051. Woelflin- Dec. 14', 1937 2,151,963 Eladmark Mar; 28; 1939 2,169,369 Osterlok Aug; 15, 1939' 2,097,121 Fromm -0ct..26,- 1937 2,304,304 Fritz' Dec. 8, 1942 FOREIGN PATENTS Number 2 Country Date 473,643 Great Britain Oct. 18, 1937 OTHER REFERENCES Canadian Chemistry and Process Industries,

Jan. 1940,11. 29.

Paper Trade Journal, June 23, 1938, p.-.18.

The Manufacture of Pulpandchemistry, vol; 4, 3d ed., 1938, Sec. 5, p.=28; vol. 5, '25 1,.ppl 100-101.

PulpandPaper Magazine of Canada, Nov; "27, 1919, pp. 10221-1023.

3d 'ed., 1939, Sect 

